Abrasive work back-up to recondition doctor blade



ABRASIVE WORK BACK-UP T0 RECONDITION DOCTOR BLADE Filed Aug. 29, 1962 P.T. KUHNEL July 20, 1965 3 Sheets-Sheet 1 July 20, 1965 P. T. KUHNEL3,195,500

ABRASIVE WORK BACK-UP TO RECONDITION DOCTOR BLADE Filed Aug 29, 1962 3Sheets-Sheet 2 July 20 65 P. T. KUHNEL 3,195,500

ABRASIVE ,WORK BACK-UP TO RECONDITION DOCTOR BLADE Filed Aug. 29, 1962 3Sheets-Sheet 3 United States Patent 3,195,500 ABRASIVE WORK BACK-UP T0RECONDITIQN DOCTOR BLADE Paul T. Kuhnel, Neenah, Wis., assignor toKimberly- Clarlr Corporation, Neenail, Wis, a corporation of DelawareFiled Aug. 29, 1962, Ser. No. 220,247

2 Claims. (Cl. 118-70) This invention relates to improvements in coatingequipment and procedures and is particularly concerned with the coatingof paper webs and the like.

In many coating processes a resiliently covered backing roll supports atraveling Web of paper as the web is directed between the backing rolland a flexible blade pressured against the backing roll and web. The webbefore reaching the blade is provided with an excess of coatingcomposition, usually an aqueous mineral coating composition. Thiscoating composition is troweled by the flexible blade to smooth some ofthe coating composition on th web while the excess of coatingcomposition is removed; the contact of the blade with the coating andweb results in significant wearing of the blade.

A principal object of this present invention is to provide a novelresiliently covered backing roll which is itself capable of honing andwearing a troweling blade at longitudinal zonal ends of the blade, wherethere is no web contact, to provide substantially uniform blade wearover the blade length; further, the novel resilient backing roll hasbeen found to support the traveling paper web in such manner thatwrinkles in the web as the Web moves under the blade are substantiallyavoided.

A particular object of the invention is to provide a novel combinationof backing roll and blade in which characteristics of the backing rollimprove the operating life of the blade and permit the coating ofvarious web widths without blade change.

An important object of the present invention is the provision of a novelprocess for carrying out blade coating operations.

The invention will be more fully understood by reference to thefollowing detailed description and accompanying drawings wherein:

FIG. 1 is a schematic view of one form of coating device useful in thepractice of the invention;

FIG. 2 is a perspective view of the backing roll-blade combination ofFIG. 1 with the metering mechanism removed and particularly illustratingthe relationship of backing roll, web, and blade;

FIG. 3 is a view of the blade and holder of FIG. 1 particularlyillustrating the cooperative relationship of the blade, web, and backingroll;

FIG. 4 is a fragmentary plan view of the blade of FIG. 3 illustratingblade wear;

FIG. 5 is a view similar to that of FIG. 2 but with the roll carrying amuch wider web;

FIG. 6 is a view similar to that of FIG. 2 but with the roll carrying amuch narrower web; and

FIG. 7 is a View of a portion of the structure of FIG. 2 particularlyillustrating support mechanism for pivotal and oscillating movement ofthe blade holder.

While reference is made in the following detailed description to asingle coating application to one side of a paper web in an operation ona papermaking machine, the principles of the invention are equallyapplicable to coating the second side of the web on the machine, tomultiple superposed coating applications, and to similar coatingapplications on an oif-the-machine coater.

Referring to the drawings and initially in particular to FIG. 1, thenumeral 1 designates a freshly formed paper web of a conventionalprinting paper furnish traveling as on a papermaking machine atpapermaking speed over a guide roll 2 to a backing roll 3 and through apressure nip 4 formed between the backing roll and an applicator roll 5.Coating composition from a pond 6 is applied to the applicator roll 5 bymetering rolls 7, 8 rotating in the direction indicated by the arrows.Coating composition is directed to the pond 6 through an inlet 9positioned above the pond and supplied by any suitable source (notshown). Backing roll 3 and coating applicator roll 5 are longitudinallycoextensive and independently driven at substantially the same speed inopposite rotational directions as indicated by the arrows. Web 1 travelsat substantially the speed of the backing roll. Backing roll 3 isresiliently covered, of about 30" diameter, and rotates at a speed of600 f.p.m., for example, while applicator roll 5 is of a similardiameter and resiliently covered as indicated; applicator roll 5 may beof chrome plated steel, if desired. The backing roll and applicator rollin usual practice may have an axial length in the range of 30 to 250"-aaconventional length being about 144.

The coating composition is carried in film form on the applicator rollto the nip 4 where an excess of coating is applied to the traveling webin the nip. The pressure between the applicator roll and the backingroll controls the quantity of coating applied to the web, and thepressure is usually a light positive pressure of between about 2-20pounds per lineal inch.

The traveling Web 1 is carried from the nip 4 on the resiliently coveredbacking roll 3 to a second nip 10 formed between the backing roll and aflexible blade 11. Blade 11 serves to trowel some of the coatingcomposition on to the web and to remove excess designated at 12; thisexcess drains off over a coating composition deflector 15 to a receiver13 positioned below the applicator roll 5 and may be recirculated. Theweb passes from the blade over a guide rol 14 in the direction indicatedby the arrow to conventional dryers.

Flexible blade 11 is of spring steel of about Rockwell C hardness of47-51 and quite thin, usually between about 0.012" and'0.024". Thisblade extends longitudinally of the backing roll (FIG. 2) and projectsbeyond the backing roll at each backing roll end for a distance ofabout 1. However, if desired, the blade may be from /2 to 1 narrowerthan the backing roll face and arranged to preclude development of lipoverhang. The blade 11 is supported by a holder 16 from which it extendsabout to 1" in usual practice. This blade is pressured to the backingroll by any conventional mechanism, one form of which is illustrated inFIG. 2 and discussed hereinafter. Under pressure the blade flexestransversely, as indicated in FIG. 1, and also flexes longitudinally toconform to the web and backing roll configuration. The blade, prior toinstallation, is suitably honed to assist initial conformation of theblade with the roll; further, the resiliently covered roll is itselfdeformed slightly (FIG. 3) under blade pressure and the blade tip isquickly worn in by the traveling web-coating combination so thatintimate contact is attained at nip 10. The web itself, tensioned aroundthe backing roll and wetted by the coating composition, is elongatedlocally and stretched by the blade action.

Blade wear causes a decrease in the projection of the blade from theholder; such wear may conventionally be A on an original projectionwithout blade change. This tends to lead to non-uniform coating sincethe wear occurs substantially only where the blade contacts the web.

The bipartite blade holder 16 (FIG. 2) is suitably retained as a unit bybolts 17 and is suitably retained as a unit by bolts 17 and is supportedon a lower carrier member 18 by alternate threaded bolts 19. The carriermember (FIG. 2) carries on opposite sides pivot shafts 20 (one shown)which arereceived bearings 21 to" provide for pivotal movernen'tofthe'holder toward and away from the backing roll while shaftenlargements 20a (one shown) restrain the carrier against longitudinalmovement relative to thelbearing. Fluid pressure means designatedgenerally at 22 and comprising air cylinders.

are secured on pivot joints 23 between platforms 24 and lever. arms 25on opposite rearward sides of the carrier 4; out the coverbody. Thus thepaper web is'carried on a grit-filled or'abradant surface in which amyriad of abrasive grit grains are surrounded and embedded in therubmember 18 for urging the holder pivotally to the back-' ing roll 3and the web 1- carried thereon. Platforms 24 are supported forrectilineal movement with end mounts 26 which are integral with across-member 27;" end. mounts 26 each have a sliding engagement withapair of short parallel rods 28 through the medium-of bushings 31. Eachpair of rods 28 is fixedly retained by an upstanding support 29 of abase 30, and theparallel rods prevent rotation of the end'mounts 26 andbearings 21 which latter are retained positioned on the end mounts.

Control ofcylinder pressure'effects the control of'the.

pressure of the blade on the backingroll and web. Since the blade isflexible longitudinally and transversely,jthe

blade bears against the backing roll at the ends despite the paperthickness which usually isabout 0.003". To minimize wear of. theresilient 'coverby the bladeoni the roll end zones 32, 33, water sprays35, 36 are provided adjacent eachend ofthe roll. Such sprays also serveto insure against coating composition buildup n the roll end zones andmay be adjustable to provide for varying lengths of the end zones."Additionally, to extend the.

longitudinal wear zones of the blade in the vicinity of the junctures37, 33 of the web and end zones 32, 33, the blade is oscillatedlongitudinally of" the roll; for this purpose the right hand end mount26 (FIG. 2) receives coating operations.

bery or elastomeric compound, Preferably, the grit grains 'cover to ofthe surface of the backing roll. The grains are, however, discreteparticles, resiliently'embed.

' simply from surface friction'etfects or fromother physicalcharacteristics of the grit surface is not readily deter minable. In anyevent, the draws through thecoating device are improved. Y

The grit which provides the abradant surface may'vary in size, inproportions present,: andin specific'nature, that is, it may be aluminumoxide, silicon dioxide, silicon carbide, or the like. Since the specificnature of the blade, blade pressure, the nature of the web, machinespeed, and the coating'composition affect the blade Wear rate, the gritsize and proportions shouldbe selected ;to wear the blade in theextremities .46, 47 at the same rate as in the medial portion 48. Theoptimum conditions are readily determinable by simple test for anyspecific set ofconditio'ns.

oscillator rod 39 which, through pin 40,- is connectedto cam 41 andmotor-gear box combination 4 2, 43. By

such blade oscillating means the blade is worn moregraduallylongitudinally by the Web'at the junctures 37, 38.

However, oifsets, such as designated at45 in FIG. '4 by V v the dashedline, develop and limit the utility of the blade for use with other webwidths; also, blade wear from the original blade tip 44 at the bladeextremities 46, 47 is much less thanvin the blademedial portion 43'(FIG. 2). Accordingly, blade pressures tend to vary. along the bladelength during operation. and. this'requires blade changeat frequencyintervals. Further, when blade high spots develop in the end zonesrelative to the blade,

medial portion, the amount of composition applied tends to increase,resulting, as'already noted, in nonuniform coating application over thelength of the web. 7

The specific blade pivotal and oscillating mechanism shown isillustrative only and forms no part of thepresent invention; other bladeoscillating apparatus and blade pressure devices, of which-many arecommonly employed, are useful in the practice of the invention. 7

In the practice of this invention, at least the roll end zones 32, 33,that is, the peripheral area of the rolls which are'not covered by thepaper web, are roughened and are composed of a resilient rubberycompound which 'in-. This grit in the' cludes a portion of abrasivegrit. roll surface serves to Wear the blade extremities 46, 47 tosubstantially the same extent as the combination of web and coatingcomposition etfectwear in the blade medial portion 48. Such arrangementinhibitsagainst the development of the offsets in the blade designatedat 45 (FIG; 4) and results in uniform blade wear indicated by thestraight dashed line 4-9 in FIG. 4.

The use of blade oscillation with mechanism .such as 5 previouslydescribed tends to aid uniformity of blade wear;

the blade longitudinal movement'is very slow compared} Grits of aluminumoxide having a mesh of between about 100 to 400are generally useful andmay be present ,to'the extent of from about 15% by weight; of the cover'50 to about 50%. The grit specific gravity is usually greater than andabout twice the density of the rubber in which it is embedded. Thelarger size. grit, mesh (about 150 microns), provides-a coarsesurface;.a smaller size grit, 325 mesh (about 43 microns), providesa'somewhat more uniform surface-overall forthe same weight or grit. A325 mesh grit to the extent of about 15% by weight ofthe rubber cover 50(Pusey and Jonesplastometer density of 67) has been found to be verysatisfactory for minimizing Web wrinkles on the roll in advance of theblade in the specific apparatus arrangement de-- scribed. Under theconditions specifically described herein, about 25 to 30% by weight ofaluminum oxide grit of amesh of about 220 appears to provide, optimumblade wear (about 0.003" per hour) and weblcontrol also 1 when cover 50has a P and J .of about 67.

' in backing. rolls.

, be in the conventional rangeof, stock density forrubber covered rolls,that is, from about 30 to' upto 150 and usually lies in the range of 60to The stock is compounded with the grit therein so that it isthoroughly dispersed andinterrnixedjthe stock is applied to the shelland tie plyand, after curing, is ground true to provide a peripheralsurface of uniform'diameter with the grit randomly exposed. 7

Referring now to FIG. 5, since the blade is worn uniformly over itslength in the course of a coating operation (FIGS. 1 and 2), the widerwidth web55 (FIG. 5) may be" substituted. and coated without bladechange.

. Similarly, if desired, a narrower width web 56 may be employ'ed. Morespecifically, blade wear does not impose limitations on thesuccessioniof widths which'may be coated-without blade change. 7, V 7

It is to befnoted that even though the blade" extremities are worn bythe action of the novel roll, it isistill desirable toutilizethewatersprays on the roll edges; such protects the roll againstwear and cools the blade as well as pre-' 7 Most suitably, the backingroll 1 in the peripheral'resilient coverporti0u 50 includesgritj'SIL'distributed throughventing coating buildup on the roll endzones. 7 I

The coating compositions which may be employed are those customarilyuseful in the coating of paper webs and may include clays, fillers,binders, and the like. Typical of such a composition is the following:

Parts by weight Clay 70 Sodium hexametaphosphate 0.2 Calcium carbonate30 Caustic 0.2 Starch 17 Calcium stearate 0.5 Water sufiicient to make58% solids.

Viscosity, 3000 centipoises.

By way of specific example, the web to which such coating is applied mayhave a basis weight uncoated of about 55 pounds, basis weight beingpredicated upon 500 sheets 25"x38". The coat weight applied may be about12 pounds per side depending somewhat upon the lineal pressure of theblade on the backing roll. Such pressure may be controlled to achieveparticular results between about 1% to 9 pounds per inch.

It is to be noted that it is known in the coating field to extend thelife of backing rolls by providing end sleeves which may replace wornroll ends. Such sleeves are rubber covered in the same manner as themain roll body. It is contemplated that such sleeves may incorporategrit in accordance with the practice of this invention.

The rate of wear of a conventional blade pressured against a webcarrying coating compositions of the general type described is dependentupon a plurality of factors but has been found to be very generallyabout 0.003" per hour. thus develops in an hour of running an oifset orblade 10w spot equivalent to about paper web thickness. This wear, inthe medial portion of the blade, is uniform over the medial portion and,if permitted to continue, results in poor roll life due to higherpressures exerted by the blade in the unworn blade extremities. By thepractice of the present invention, roll life is itself extended due touniform application of pressure throughout a coating operation and, infact, throughout continued coating operations with the same blade.

The blade itself may also be honed over its length initially by runningit against the roll prior to presentation of the web to the backingroll-thus eliminating time consuming honing operations preliminary toblade mounting.

Foreign particles do not tend to accumulate in the roll surface as thedeforming action of the blade exerted on the resilient matrix in whichthe grit particles are embedded, followed by the restoring resilientaction of the matrix, apparently tends to aid maintaining the rollsurface clean.

With the grit distributed in uniform but substantially randomly orientedand haphazard arrangement through the resilient backing roll cover, anywear of the cover itself continuously exposes new abrasive granules tothe blade since the pressure on the blade continuously urges the bladeand roll into intimate engagement.

In the specific description set forth hereinbefore, the ap- Such ablade, usually of stainless or spring steel,

plicator roll 5 has been indicated to be in light positive pressuredengagement with the backing roll; such is not necessary and the usualpan type applicator roll wherein a considerable excess of coating isprovided to the applicator roll-backing roll nip may be employed.However, in such instances the nip may be zero pressure and may be openas much as 0.060". However, even where the positive pressure exists asin the instance of FIG. 1, the pulverulent nature of the grit particlesdoes not adversely affect the applicator roll as long as the roll speedsare approximately the same.

It will be understood that this invention is susceptible to modificationin order to adapt to different usages and conditions and, accordingly,it is desired to comprehend such modifications within the invention asmay fall within the scope of the appended claims.

What is claimed is:

1. The combination in a coating device for a traveling paper Web or thelike, of a longitudinally extending backing roll having a resilientdeformable peripheral cover for supporting a traveling web Wrappedtherearound, a longitudinally and transversely flexible doctor bladeextending axially with said backing roll and defining with said backingroll a nip through which said web passes, means for urging said doctorblade against the backing roll and a web thereon to load the flexibledoctor blade against the roll and web, means on the oncoming side of thenip for applying an excess of coating composition to the side of the webon which the doctor blade bears, said doctor blade extendingsubstantially the full length of said backing roll and exerting apressure against said backing roll and traveling web which locallydeforms the web and the backing roll over the length of the backingroll, and said backing roll being characterized by a grit containingsurface which wears said doctor blade in portions of the backing rollexposed to the doctor blade and which surface also provides traction forthe traveling web.

2. The combination as claimed in claim 1 and in which water sprays arepositioned to apply w-ater to the backing roll in the said portions ofthe backing roll which are exposed to the doctor blade.

References Cited by the Examiner UNITED STATES PATENTS 1,787,890 1/31Woodward 29-132 2,062,317 12/36 Joseph 29-132 2,155,083 4/39 Drewsen.2,280,208 4/42 Wilkie 29-132 2,297,128 9/42 Benson 226-193 2,534,32012/50 Taylor 118-126 3,080,847 3/63 Justus 118-126 FOREIGN PATENTS643,764 9/50 Great Britain.

RICHARD D. NEVIUS, Primary Examiner.

1. THE COMBINATION IN A COATING DEVICE FOR A TRAVELING PAPER WEB OR THELIKE, OF A LONGITUDINALLY EXTENDING BACKING ROLL HAVING A RESILIENTDEFORMABLE PERIPHERAL COVER FOR SUPPORTING A RESILIENT DEFORMABLEPERIPHERAL COVER LONGITUDINALLY AND TRANSVERSELY FLEXIBLE DOCTOR BLADEEXTENDING AXIALLY WITH SAID BACKING ROLL AND DEFINING WITH SAID BACKINGROLL A NIP THROUGH WHICH SAID WEB PASSES, MEANS FOR URGING SAID DOCTORBLADE AGAINST THE BACKING ROLL AND A WEB THEREON TO LOAD THE FLEXIBLEDOCTOR BLADE AGAINST THE ROLL AND WEB, MEANS ON THE ONCOMING SIDE OF THENIP FOR APPLYING AN EXCESS OF COATING COMPOSITION TO THE SIDE OF THE WEBON WHICH THE DOCTOR BLADE BEARS, SAID DOCTOR BLADE EXTENDINGSUBSTANTIALLY THE FULL LENGTH OF SAID BACKING ROLL AND EXERTING ASPRESSURE AGAINST SAID BACKING ROLL AND TRAVELING WEB WHICH LOCALLYDEFORMS THE WEB AND THE BACKING ROLL OVER THE LENGTH OF THE BACKINGROLL, AND SAID BACKING ROLL BEING CHARACTERIZED BY A GRIT CONTAININGSURFACE WHICH WEARS SAID DOCTOR BLADE IN PORTIONS OF THE BACKING ROLLEXPOSED TO THE DOCTOR BLADE AND WHICH SURFACE ALSO PROVIDES RACTION FORTHE TRAVELING WEB.